Stepping on the Gas: Pathways to Reduce Venting in Household-Scale Kenyan Biogas Digesters

Abstract

One method of producing bioenergy is through Anaerobic Digestion (AD) of plant, animal, and human waste in a biodigester. AD is a cost-effective method of simultaneously managing harmful waste, creating biogas for cooking, and producing nitrogen-rich liquid fertiliser for agriculture. However, there is minimal exploration around how these household-scale biogas digesters, in Kenya and beyond, contribute to global bioenergy methane emissions - this paper directly addresses this gap.

We employ a two-phase approach which establishes the scale of the challenge through a rapid review of available literature on loss, leaking and venting, then contextualise this data with the lived experience of 33 biogas-users across 5 counties in Kenya.

The results highlight three critical dimensions - the demand, supply, and systemic from the users' perspectives - all linked to the venting phenomenon. The demand side showed a lack of understanding of venting and its causes, these included; pre-processing feedstock, feeding regime, seasonal influence, pressure, cookstove stacking, lack of maintenance and market access. On the supply side, our critical learning highlighted that biogas units are typically sold based upon the available feedstock, rather than the potential gas need. Next, we identify the systemic drivers; household-scale digesters do not pose a climate threat, a lack of technical solutions, and the overwhelming Pandora's Box of impacts. For each driver - the supply, demand, and systemic - we highlight a series of mitigating actions that small-scale, locally-led biogas stakeholders can take to minimise venting, this is summarised in our practical “venting framework”.